The invention relates to processing video signals representing a sequence of images in which two adjacent image lines each exhibit identical video contents.
Such image sequences are obtained for example by discarding every second field in a 50 Hz field sequence, such as is usual in television technology, and reproducing in place thereof the content of the preceding field in merely line-offset (interlaced) fashion. As a result, adjacent lines of two consecutive fields have identical video contents. The consequence is that scenes photographed with a 50 Hz image sequence are effectively reproduced with only a 25 Hz image sequence and the vertical resolution is reduced. This becomes unpleasantly apparent to a viewer, in particular on large-format displays, as stairstep effects or flicker along edges running obliquely in the image.
Such artifacts can be at least diminished by suitable image-processing techniques applied in receiver-side fashion, provided, however, that such video signals or image sequences having linewise repeated data are recognized as such, especially since these are not specially identified by the program provider.
There is a need for a technique of detecting image sequences having linewise repeated video data.